全文获取类型
收费全文 | 13991篇 |
免费 | 1237篇 |
国内免费 | 443篇 |
专业分类
化学 | 2662篇 |
晶体学 | 58篇 |
力学 | 6517篇 |
综合类 | 87篇 |
数学 | 2510篇 |
物理学 | 3837篇 |
出版年
2024年 | 3篇 |
2023年 | 131篇 |
2022年 | 180篇 |
2021年 | 274篇 |
2020年 | 373篇 |
2019年 | 283篇 |
2018年 | 332篇 |
2017年 | 356篇 |
2016年 | 389篇 |
2015年 | 423篇 |
2014年 | 549篇 |
2013年 | 1020篇 |
2012年 | 721篇 |
2011年 | 914篇 |
2010年 | 627篇 |
2009年 | 822篇 |
2008年 | 793篇 |
2007年 | 809篇 |
2006年 | 716篇 |
2005年 | 614篇 |
2004年 | 646篇 |
2003年 | 547篇 |
2002年 | 489篇 |
2001年 | 359篇 |
2000年 | 326篇 |
1999年 | 261篇 |
1998年 | 279篇 |
1997年 | 277篇 |
1996年 | 259篇 |
1995年 | 259篇 |
1994年 | 234篇 |
1993年 | 213篇 |
1992年 | 208篇 |
1991年 | 156篇 |
1990年 | 141篇 |
1989年 | 113篇 |
1988年 | 104篇 |
1987年 | 68篇 |
1986年 | 70篇 |
1985年 | 78篇 |
1984年 | 70篇 |
1983年 | 38篇 |
1982年 | 76篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1971年 | 6篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Since the (original) ghost fluid method (OGFM) was proposed by Fedkiw et al. in 1999 [5], a series of other GFM-based methods such as the gas–water version GFM (GWGFM), the modified GFM (MGFM) and the real GFM (RGFM) have been developed subsequently. Systematic analysis, however, has yet to be carried out for the various GFMs on their accuracies and conservation errors. In this paper, we develop a technique to rigorously analyze the accuracies and conservation errors of these different GFMs when applied to the multi-medium Riemann problem with a general equation of state (EOS). By analyzing and comparing the interfacial state provided by each GFM to the exact one of the original multi-medium Riemann problem, we show that the accuracy of interfacial treatment can achieve “third-order accuracy” in the sense of comparing to the exact solution of the original mutli-medium Riemann problem for the MGFM and the RGFM, while it is of at most “first-order accuracy” for the OGFM and the GWGFM when the interface approach is actually near in balance. Similar conclusions are also obtained in association with the local conservation errors. A special test method is exploited to validate these theoretical conclusions from the numerical viewpoint. 相似文献
992.
A class of new benchmark deformational flow test cases for the two-dimensional horizontal linear transport problems on the sphere is proposed. The scalar field follows complex trajectories and undergoes severe deformation during the simulation; however, the flow reverses its course at half-time and the scalar field returns to its initial position and shape. This process makes the exact solution available at the end of the simulation, and facilitates assessment of the accuracy of the underlying transport scheme. A procedure to eliminate possible cancellations of errors when the flow reverses is proposed. 相似文献
993.
The backward phase flow and FBI-transform-based Eulerian Gaussian beams for the Schrödinger equation
We propose the backward phase flow method to implement the Fourier–Bros–Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schrödinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in [12]. In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying the FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms. 相似文献
994.
This paper develops the basic analytical theory related to some recently introduced crowd dynamics models.Where well posedness was known only locally in time,it is here extended to all of R+.The result... 相似文献
995.
The original BML model is extended by introducing extended sites, which can hold several vehicles at each time-step. Unexpectedly, the flow in the extended model sharply transits from free-flow to global jams, but the transition is not one-order in original BML model. And congestion in the extended model appears more easily. This can ascribe to the mixture of vehicles from different directions in one site, leading to the drop-off of the capacity of the site. Furthermore, the typical configuration of free flowing and global jams in the extended models is disorder, different from the regular structure in the original model. 相似文献
996.
AA Yan LI Kai CAO ZhongHua & HU WenRui Key Laboratory of Microgravity 《中国科学:物理学 力学 天文学(英文版)》2011,(2)
The dependency of the critical Marangoni number on the geometrical aspect ratio of the floating half zone is essential to predict the onset of oscillatory thermocapillary convection.The experimental studies in the microgravity conditions on floating half zones of several centimeters in diameter have predicted that the critical Marangoni number increases with the increasing aspect ratio,and the terrestrial experimental studies have predicted the contradictory conclusion for floating half zones of several mil... 相似文献
997.
Yuhiro Iwamoto Hiroshi Yamaguchi Xiao-Dong Niu 《Journal of magnetism and magnetic materials》2011,323(10):1378-1383
The magnetic body force in boiling two-phase temperature-sensitive magnetic fluid (TSMF) flow is known to effectively increase the driving force of magnetic fluid in a non-uniform magnetic field. Based on this mechanism, in the present study, a binary TSMF, which is a mixture of the TSMF and a low-boiling-saturation-temperature organic solution, is proposed to be used in a heat transport device to enhance its circulation. In order to see its performance in the heat transport device, the pressure difference at different heated temperatures, magnetic fields and inclination angles of the heating section are investigated experimentally and theoretically. Results showed that the driving force increases remarkably due to more gas phase appearing in the test fluid and the magnetization of it decreasing. At low magnetic field the driving force is enhanced greatly when the inclination angle is close to 60°, while at high magnetic field the driving force is remarkably enhanced due to the effect of the magnetic force in the inclination angle range from 0° to 30° and 60° to 90°. 相似文献
998.
《Current Applied Physics》2014,14(3):378-382
Nanolayered superlattices composed of ferromagnetic SrRuO3 and antiferromagnetic SrMnO3 layers were grown on SrTiO3 (100) substrates by pulsed laser deposition. Multilayers were grown under predetermined synthesis conditions resulting in growth of SrRuO3 and SrMnO3 by step flow and layer-by-layer modes, respectively. The growth of SrMnO3 was observed to occur through the layer-by-layer during the entire deposition process despite the expected increase in surface roughness because of the incorporation of SrRuO3 upper layers. Monitoring by reflection high-energy electron diffraction (RHEED) revealed that the growth of every SrMnO3 layer consisted of a pre-stage during which the gaps on the relatively rough SrRuO3 surface were filled before the actual growth of the SrMnO3 layer, which resulted in incomplete half oscillation and change from spot patterns to streaky patterns. The in-plane lattice constant did not show any considerable change in the case of SrRuO3 and SrMnO3 layers, despite the considerable lattice mismatch between the two materials (SrRuO3, SrMnO3) and SrTiO3. On the other hand, the RHEED patterns showed the existence of lattice mismatch effects in the out-of-plane lattice constant, which showed significant strains of opposite signs in the different layers, indicating a strong dependence on the composition of the layers and superlattice periodicity. In this paper, the growth characteristics of a SrRuO3/SrMnO3 multilayer along with its magnetic properties will be discussed. 相似文献
999.
In this Letter, a car-following model with consideration of roadside memorial is proposed. The numerical results show that the proposed model can qualitatively describe the impacts of roadside memorial on traffic flow and the traffic risk coefficient. It is also shown that roadside memorial can enhance the traffic safety. 相似文献
1000.